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Not very happy with LEDs.

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ClydeCrashKop

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24V G4 SMD LED Disk Internal circuitry provides constant current draw regardless of voltage fluctuations from the source (20 to 32 VDC for 24V models), meaning no flickering and longer LED life.
https://www.doctorled.com/store/LED-Bulb/24V-LED-Bulb/24V-G4-SMD-LED-Disk
Dr LED.jpg

We got 140 of these from West Marine. 30 or more burnt the rectifier diodes and stunk and quit. At least 7 of them blew the 7 amp fuses. West Marine was good about replacing them. Some that were working okay were left on in a room with the A/C off. They got so hot that they melted the solder and the disk fell off its pins.
LEDs burnt sm.jpg


We got some 24 volt LED rope lights for under the stairs. I replaced the incandescent strings on 2 stairs. 3 months later, more incandescent strings went bad so I replaced the rest of them. With only occasional use, the LEDs that I had already replaced were a lot dimmer than the new ones from the same spool. So I replaced those 2 strings again and told the captain not to use them unless the owner was onboard.

Faded LEDs sm.jpg
 

RODALCO

Well-Known Member
Pretty bad , fire hazard too, they look well made, but unknown origin probably. I had problems with 240V e14 led bulbs in a rangehood which lasted only 3 months. Replaced them with 12 V led strips which are going strong on a 240/12 V transformator.
 

RODALCO

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audioguru

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Why did you use rectifier diodes? The spec's say 24VDC, not 24VAC that has a peak voltage of 34V.
The spec's do not say how to cool the discs, liquid nitrogen maybe.
 

Externet

Active Member
Is there a chance they are 12VDC mislabeled as 24V ? Give a few a try for longevity, heat and luminosity on 12VDC
 

audioguru

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If they have the eight white LEDs in series then they will not light with only 12V since a white LED needs about 3V. If they light with 12V then they are connected in two series strings of four LEDs.
Are there any current-limiting parts on the circuits? I betcha not.
 

Tony Stewart

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It seems G4 only defines the 4mm pitch of the pins and for preference in different counties there were 12Vac and 24Vac type halogens.

For compatibility now G4 LEDs are made to adapt to one or the other.
They all tend to use 4 discrete Schottky diodes must be labeled with the Vdc rating.

For 24Vac = 34Vp , and if using 8 in series would be OFF @ 20 Vdc, DIM @ 23Vdc , then with a choice series R in the 30-40 Ohm range would MAX @31Vdc. With a transformer rated for Halogen bulbs, the voltage would be higher than 24Vac perhaps 26V which would fit well with the RS value and 8 LEDs

For 12 Vac = 17Vp, they might use 3 LED stings with 75 Ohms and the same 4 diodes
If 4 LEDs with diodes the series R would be smaller about half of the ESR or 5 Ohms.
If 9 [email protected]/dc They would be 3S3P with string Rs values in the range of 75 Ohms with diodes.

My hunch is that the reason for failures is PLT or power line transients not bad LEDs.

All Schottky diodes with lower forward voltage (lower ESR) also have lower PIV rating from the same style, vendor & size. e.g. 20,30,40V.... due to gap length.

But the luminaires may not have MOV's. This is a customer power quality issue.

But there are many many variations of G4 LEDs.


Next is 230Vac


next is 12Vdc only with a simpler Switching regulator
http://miniimg4.rightinthebox.com/images//201303/tuazya1362129984549.jpg
http://miniimg3.rightinthebox.com/images//201303/drrgmn1362129984085.jpg
 

alec_t

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They have 4 little diodes on the back
Nothing else? Then what magic performs this advertised feature? :-
  • Internal circuitry provides constant current draw regardless of voltage fluctuations from the source (20 to 32 VDC for 24V models), meaning no flickering and longer LED life.
 

DerStrom8

Super Moderator
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I vaguely remember Dave Jones from the EEVblog doing a review on similar LEDs, and he had similar experiences.
 

MrAl

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24V G4 SMD LED Disk Internal circuitry provides constant current draw regardless of voltage fluctuations from the source (20 to 32 VDC for 24V models), meaning no flickering and longer LED life.
https://www.doctorled.com/store/LED-Bulb/24V-LED-Bulb/24V-G4-SMD-LED-Disk
View attachment 100928

We got 140 of these from West Marine. 30 or more burnt the rectifier diodes and stunk and quit. At least 7 of them blew the 7 amp fuses. West Marine was good about replacing them. Some that were working okay were left on in a room with the A/C off. They got so hot that they melted the solder and the disk fell off its pins.
View attachment 100929


We got some 24 volt LED rope lights for under the stairs. I replaced the incandescent strings on 2 stairs. 3 months later, more incandescent strings went bad so I replaced the rest of them. With only occasional use, the LEDs that I had already replaced were a lot dimmer than the new ones from the same spool. So I replaced those 2 strings again and told the captain not to use them unless the owner was onboard.

View attachment 100930
Hi,

Sad. I find that the only way to get some things to work right is to modify it myself. If i want the product then i have no choice because sending it back means i dont have the product anymore.

So my advice would be to completely analyze the circuitry and make the necessary changes, then start using with confidence.

I am assuming you can get to and examine all the parts. Perhaps you can post a few close up pics of the board front and back, and might have to remove some parts to see the traces. Or if you traced the circuit post the schematic here and we can redesign it so it works for 10000 hours or more.

It sounds like an inexperienced designer made those lights. Some think that you can apply a known regulated voltage and be done with it. That's a way to burn them all out.
I got a flashlight once that kept burning out the LEDs. It was a supposedly good company too called Streamlight.

This happens a lot these days.
 

Tony Stewart

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Nothing else? Then what magic performs this advertised feature? :-
  • Internal circuitry provides constant current draw regardless of voltage fluctuations from the source (20 to 32 VDC for 24V models), meaning no flickering and longer LED life.
This looks like a translation error from engineering or supplier to online sales
With general purpose diodes with [email protected] , with a case rated for 60 mW has a differential resistance or ESR of about 16 Ω each.
These LED look the size with 10Ω ESR x8 , so total ESR could be 80 +16 +16= 112 Ω and a 20 to 32 V rise of 12V would result in about 100mA rise from Off. or a total power then of 3.2W

These are dimmable but only constant current when the voltage is constant :woot: Don't Ya luv low tech sales ads.
 

ClydeCrashKop

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I tried them on 12 volts and they were very dim.
We are using 24 volt transformers but I put full wave bridge rectifiers on their outputs, just in case and to bring the 26 or 27 volts down a little. But that is well below the 32 VDC they claim.
All of the diodes have blisters on the clear coat.
The 6 pin IC is numbered 40??

LED back.jpg
 

alec_t

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We are using 24 volt transformers but I put full wave bridge rectifiers on their outputs, just in case and to bring the 26 or 27 volts down a little.
Where did you get 26 or 27V? As AG pointed out, 24VAC has a peak of 34V. If your tranny is poorly regulated and putting out 27VAC (RMS) then the peak would be 38V. Even with a diode bridge you'd be subjecting the LEDs to peaks of ~ 36.8VDC.
 

audioguru

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It looks like the rectifier diodes are failing first, not the LEDs. Maybe the diodes become shorted then the entire circuit becomes destroyed. Maybe the diodes are zener diodes by mistake, then they conduct a very high current from the transformer and get very hot.
 

Tony Stewart

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The problem with linear constant current sources is they must dump VI product in heat for every volt above threshold. Is this board aluminium? or epoxy/fiberglass typ.

Is it possible instead of 1P8S this board is 2P4S ( 2 strings of 4) Therefore it would be half the voltage range.
The LEDs are still good. and show now signs of phosphor burns.

Maybe Bad specs.

IMHO this device should have been rated for 13~16Vdc or 12vac which at low load ~14Vac and burn up at 24Vac
 
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